An antifoam agent is typically added to oils to reduce foaming and air entrainment. Antifoams are common additives in many types of lubricating oils and hydraulic fluids. The purpose of the antifoam is to retard the formation of stable foam on the surface of the oil in the sump, gearbox, or reservoir. Silicones, or compounds containing silicone, and acrylic copolymers are popularly used in mineral-based lubricant formulations. Lighter grade turbine oils and hydraulic fluids are generally formulated with acrylate antifoam additives while heavier gear oils, paper machine oils, and crankcase lubricants may use silicone.
For the antifoam agents to be effective they need to have limited solubility in the lubricant in which they are added. As lubricating base stocks have become more highly refined the solubility has decreased to a point where it has been increasingly difficult to hold antifoams in suspension without the addition of a solubilizing agent.
There exists a need to increase the effectiveness of antifoam agents.